The survey, taken by Public Policy Polling for the liberal website Daily Kos, shows Johnson holding an 11-point advantage over Feingold, 52 percent to 41 percent. Seven percent were undecided.

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It’s the largest polling lead Johnson has held since he clinched the state Republican Party’s endorsement back in May, and a jarring deficit for the state’s junior senator in the traditionally deep blue state.

PPP chalks up Johnson’s advantage to “an enormous enthusiasm gap” and a “malaise with Democratic voters” – a lethal combination for a state where President Barack Obama defeated Sen. John McCain by a breezy 14 points just two years ago.

“Wisconsin is seeing one of the most severe enthusiasm gaps in the country. If turnout matched 2008 Johnson would be leading Feingold only 47-46,” wrote PPP’s Tom Jensen, noting that if Democrats “wake up,” the Badger State has the potential to become a toss-up.

Democrats have attempted to paint the self-funding Johnson as an extremist who believes Social Security is a “Ponzi scheme” and blames global warming on “sunspot activity,” but the PPP survey indicates that 46 percent of likely voters view the plastics manufacturer favorably. Meanwhile, just 40 percent approve of Feingold’s job performance, according to the weekend poll, which carries a 3.8 percent margin of error.

The Feingold campaign dismissed the survey as inconsistent with other findings, and pointed to an internal poll taken before the Sept. 14 primary. That survey showed Feingold holding a 4-point lead among likely voters, 47 percent to 43 percent.

“Kos is auto-calls on a Saturday and Sunday during the Badgers and Packers games,” Feingold senior strategist John Kraus told POLITICO. “You would have to buy a 10- to 15-point jump in a week for Johnson. It’s way off reality.”

But Johnson’s campaign seized on the Democratic-leaning poll as evidence that Feingold has grown out of touch with his constituents by supporting the unpopular Democratic agenda in Washington.

“This latest poll shows that voters in Wisconsin are sick and tired of the reckless spending and debt being racked up by career politicians in Washington,” said Johnson spokeswoman Sara Sendek. “Wisconsin has a clear choice between a career politician like Sen. Feingold, who continues to try to spend his way out of problems, or Ron Johnson, who has a 31-year record of growing a business and creating jobs.”

But Johnson’s record in the private sector has been under scrutiny because of his vocal critique of the Democratic stimulus bill. While Johnson told POLITICO in July “we got nothing for” the $787 billion stimulus bill, the Oshkosh Northwestern reported this week that Johnson approached a community foundation in March 2009 about tapping stimulus funds to help renovate an opera house. Feingold’s campaign is up with a blistering ad showing a string of news reports that found his plastics company received a $4 million government loan to pay for an expansion.

The spot ends with a clip of a local newscaster saying: “Ron Johnson loves to say that government doesn’t create jobs, but in the case of his own business, that doesn’t seem to be true.”

Still, Johnson’s ability to pour his own money into the race appears to be having a considerable impact, bolstering his name identification and countering Democratic attacks. The GOP nominee has unloaded more than $4.5 million on behalf of his candidacy so far, compared to Feingold’s $4.2 million.